[Xen-changelog] [xen stable-4.12] xen/x86: domctl: Don't leak data via XEN_DOMCTL_gethvmcontext

[patchbot@xxxxxxx]

commit 16803a643bc17587ac8bb37d5794cbc1a9592962
Author:     Julien Grall <jgrall@xxxxxxxxxx>
AuthorDate: Thu Mar 5 11:18:24 2020 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 5 11:18:24 2020 +0100

    xen/x86: domctl: Don't leak data via XEN_DOMCTL_gethvmcontext
    
    The HVM context may not fill up the full buffer passed by the caller.
    While we report corectly the size of the context, we will still be
    copying back the full size of the buffer.
    
    As the buffer is allocated through xmalloc(), we will be copying some
    bits from the previous allocation.
    
    Only copy back the part of the buffer used by the HVM context to prevent
    any leak.
    
    Note that per XSA-72, this is not a security issue.
    
    Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: 41d8869003e96d8b7250ad1d0246371d6929aca6
    master date: 2020-01-31 18:51:38 +0000
---
 xen/arch/x86/domctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 204928cda0..a25a849a3d 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -608,7 +608,7 @@ long arch_do_domctl(
         domain_unpause(d);
 
         domctl->u.hvmcontext.size = c.cur;
-        if ( copy_to_guest(domctl->u.hvmcontext.buffer, c.data, c.size) != 0 )
+        if ( copy_to_guest(domctl->u.hvmcontext.buffer, c.data, c.cur) != 0 )
             ret = -EFAULT;
 
     gethvmcontext_out:
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.12

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